import java.util.Scanner;

/**
 * Created with IDEA
 * author:ju bai
 * Date:2021/6/9
 * Time:16:41
 **/
public class Main2 {
    /**
     * 每日一题-客似云来
     * 斐波那契题目
     *
     * @param args
     */
    public static void main(String[] args) {
        long[] fib = new long[80];
        fib[0] = 1;
        fib[1] = 1;
        for (int i = 2; i < 80; i++) {
            fib[i] = fib[i - 1] + fib[i - 2];
        }
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            int from = sc.nextInt();
            int to = sc.nextInt();
            long count = 0;
            for (int i = from - 1; i <= to - 1; i++) {
                count += fib[i];
            }
            System.out.println(count);
        }
    }
}
